Tachistoscope



March 3,1970 JQMACQMBER I 3,498,700

TACHISTOSCOPE Filed Aug. 30, 1967 GSheetS-Sheet 1 we citfi FIG. 30

JAMES K. MACOMBER INVENTOR.

v March 3, 1970 MIACCDMBER 3,493,700

wAcnrsToscoPz 6 Sheets-Shoot 2 Filed Aug. 30, 1967 INVENTOR- JAMES K. MACOMBER 7 BY I 2 N w ATTORNEY J.IK'. MYACOMJBER 3,498,700

"March3,1970.

' mcrirsroscors 6 Sheets-Sheet 5 Filed Aug. 30, 1967 V INVENTOR.

JAMES K. MACOMBER If H ATTORNEY J. MACOMBER I v ucnismoscorn e Shets-Sheet 4.

Filed Aug. 30, 1967 I N V E N T OR JAMES K. MACOMBER ATTORNEY Mirch 3, 1970 I J K. MACoMBr-:R 3,493,700

ucmsmoscom Filed Aug. 30, 1967 6 Sheets-Sheet 5 JNVENTOR.

UAMES K. MACOMBER aa/M1 Me ATTORN m}. 3,1970 img m'ggii 3,498,700

I ncnzs wos corg Filed 11113.30, 1967 1 s Sheets-$het e IMAGE f @56 FIG /7 INVENTOR.

' FIG JAMES K. MACOMBER "ZLWQ Ma ATTORNEY United States Patent 3,498,700 TACHISTOSCOPE James Keith Macomber, Rockville Centre, N.Y., assignor to Consolidated Educational Publishing, Inc., a corporation of New York Filed Aug. 30, 1967, Ser. No. 664,517 Int. Cl. A61b 3/02 US. Cl. 351-31 21 Claims ABSTRACT OF THE DISCLOSURE This invention relates to tachistoscopes primarily for use as a part of, or an accessory for, a projector adapted to project an image on a projection screen or the like. The tachistoscope of the invention is provided with a scrambler including means to permit passage of the rays of light from the projector to the projection screen with at least one portion of the scrambler havingrefracting means to refract the rays to scramble the image at the same time permitting the scrambled rays to reach the projection screen to form an unintelligible image, and at least another portion of the scrambler being nonrefractive, such as either an open portion or a transparent portion through which an intelligible image is projected on the projection screen.

The tachistoscope has a timing mechanism which may be adjusted to produce a tachistoscopic effect by presenting the unscrambled view on the screen for short intervals of time, let us say between A and second.

This invention relates principally to tachistoscopes and the like adapted to expose visual stimuli such as figures, pictures, or words for short intervals of time for purposes in the medical and educational fields that are well known in the arts. For instance, a bright student may read slowly because of slow rate of perception due to lazy eyes. By testing the students eyes with a tachistoscope, the teacher is able to detect this defect, and frequent eye exercises, using the tachistoscope, will improve the students rate of perception and increase his reading speed.

The applicants invention is particularly concerned with tachistoscopes which are either built into or adapted for use with projectors such as slide, or film strip projectors wherein visual stimuli, projected on a projection screen by light rays from the projector, are exposed for brief periods by said tachistoscope which is interposed in the light ray path, usually between the objective lens of the projector and the projection screen.

A simple example of such a tachistoscope would be an ordinary shutter which would completely block the light rays forming the beam. of the light ray path at all times except when the shutter is open. The shutter speed could then be adjusted for flashing the visual stimuli on the projection screen for any interval desired, within the Optimum range of A1 to of a second, or any other desired interval. Such a shutter type tachistoscope which goes from complete darkness to light and then to darkness again has the disadvantage of allowing the image of the visual stimulus to persist for a longer time on the retina of the eye of the viewer due to overloading the retina by temporarily allowing too much light to be rewith the lens in focused position. The lens was then moved out of focus by moving the cam follower out of the cam dwell. The tachistoscope operated by mechanically seating the cam follower back in the cam dwell for the desired fraction of a second and then moving it out again. This projected the material on the screen in focus for the desired period of time and out of focus before and thereafter. This construction and method had the advantage of providing illumination throughout the tachistoscope run eliminating retinal overload and image persistence.

This blur to focus system still had two disadvantages. First, since there was a certain amount of blurred readability before and after the focus period, eye strain was caused by the viewer attempting to focus his eyes on an image while it is still in a blurred state. Second, since the intelligence of the stimuli should be conveyed to the viewer only during the focus period and since the blurred intervals increased the time when the viewer could recognize the image, this method had the effect of extending the recognizable exposure period before and after the time interval when the image was in focus.

It is, therefore, an object of this invention to provide a tachistoscope for a projector which will provide for substantially constant intensity of illumination on a projection screen before, during, and after the image pro jection.

Another object of the invention is to project a tachistoscope image which is always in focus when discernible.

It is also an object of this invention to provide a light ray scrambler as a component of the tachistoscope to be interposed in the light ray path between a projector and a projection screen, adapted for movement through said light ray path to present refracting portion means to scramble the light rays and non-refracting portion means to permit said light rays to reach the projection screen for the desired exposure.

It is another object of the invention to provide means to adjust the exposure time of the image to conform with exposure times usually utilized in tachistoscopes.

It is also an object of this invention to provide a smooth, positive, braking mechanism with automatic change of friction force to stop the scrambler motion, without noticeable bouncing at either slow or high speeds, after image exposure.

Another object of the invention is to provide a scrambler which renders the words or other material in the image completely unintelligible without changing the intensity of illumination appreciably on the projection screen.

A further object is to provide a scrambler which changes the image to a gray area indicating to the viewer the spot where the image is going to appear.

Another object of the invention is to maintain the area of illumination and the intensity of light in the projected area on the screen as nearly constant as practical by scrambling the image in the direction of the longest dimension of the projected area.

Another object is to provide a triggering device which is operated by squeezing two elements between the thumb and forefinger. This action applies no unbalanced force or torque to the tachistoscope since the forces between the thumb and forefinger are balanced. There is, therefore, no danger of the operator moving the projector and thereby disturbing the image during exposure.

It is another object of this invention to provide a tachistoscope which will be simple to operate, and which may be attached to existing projectors or designed into new projectors.

Further objects and advantages will appear in the specification hereinbelow.

The invention is illustrated in the accompanying drawings in which:

FIG. 1 is a side elevation of a projector system including a tachistoscope of the invention and the representation of a light ray pathway and a screen with the light ray pathway broken to save space;

FIG. 2 is a front elevation of the tachistoscope only, with parts in phantom;

FIG. 3 is a sectional view of the scram-bler of the tachistoscope as seen along the lines 3-3 in FIG. 2, with a portion of its shaft shown in full line; the sectional view does not have the usual cross hatching in order not to confuse the configuration of the surfaces 170 and 172, it being understood that surface 170 and surface 172 are the outer surfaces of the scrambler 40 shown in FIG. 3, and that the clear space between surfaces 170 and 172 is in section, the arrow in the figure representing the direction of the light ray path through the position of the scrambler;

FIG. 3A is a portion of a view similar to FIG. 3 showing a section through a scrambler having surfaces 174 and 176 with the clear space between the surfaces being considered in section;

FIG. 3B is another view similar to FIG. 3A showing a scrambler having a different cross sectional configuration with the clear space between surfaces 178 and 180 considered as being in section;

FIG. 3C is a front elevation of another form of scrambler;

FIG. 4 is a sectional view along the lines 4-4 in FIG. 1;

FIG. 5 is a sectional view along the lines 55 in FIG. 1;

FIG. 6 is an exploded perspective view with parts cut away;

FIG. 7 is a detail in front elevation;

FIG. 8 is a sectional view along the lines 8-8 in FIG. 5 with the clamp nut portions shown in plan;

FIG. 9 is an exploded perspective detail showing the brake assembly;

FIG. 9A is a detail in exploded perspective of FIG. 9 showing another form of construction for a portion of the brake assembly;

FIGS. 10 through 14 are front elevations, with parts in phantom, illustrating positions of the scrambler of the tachistoscopeand associated parts starting from the first position of rest or cocked position as shown in FIG. 10 and continuing to the second position of rest as shown in FIG. 14;

FIG. I5 is a detail view similar to that shown in FIG. 12 illustrating the trigger mechanism holding the scrambler at a fixed position;

FIG. 16 is an elevational view of a projection screen with a scrambled image projected upon it;

FIG. 17 is an elevational view of a projection screen similar to FIG. 16 with the image in focus projected upon it; and

FIG. 18 is a perspective view of an alternate form of the invention.

Similar numerals refer to similar parts throughout the several views.

The tachistoscope of this invention is provided with a main frame or housing 20 which may be incorporated into the housing 22 of the projector. It is to be understood that main frame 20 can be integral with the main housing 22 of 'the projector, or it may be supplied as a separate frame adapted to be attached to the projector housing 22 as shown in the drawings accompanying this specification. Reference to FIG. 1 shows frame 20 attached to the outside of objective lens barrel support 24 by means of a split collar 26 having a screw fastener 28 to clamp the collar 26 around the lens barrel support 24. The main frame 20 of the tachistoscope is positioned in front of the objective lens barrel 30 of the projector, and is attached to collar 26 by connecting means such as side bracket 32 as shown in FIG. 1, or by any other suitable means (such as bracket arms) between the collar 26 and the main frame 20.

The main ame 20 m y be of a y suitable size or shape adapted to hold the various elements of the tachistoscope. It is illustrated in the drawings as having a pcripheral wall 33, a front wall 34 and a rear wall 36. At present, it is preferred to manufacture the housing 20 out of a high impact plastic by any suitable molding means. However, it may be made of wood or metal or any other suitable material.

Element is a scrambling means generally referred to as the scrambler of the invention. It is comprised of at least one refracting portion 41, and a non-refracting portion 46. The refracting portion 41 is designated as having two areas 42 and 44 on both sides of the non-refracting portion 46. These may be two areas 42 and 44 of one portion 41 as shown in FIGS. 6 and 9, or may be two separate portions as shown in FIG. 3C. The non-refracting portion 46 may be clear (free from any material) as in FIGS; 6 and 9, or a transparent material as shown in FIG. 3C.

In the preferred form of the invention as illustrated in FIGS. 1 through 17 of the drawings, the scrambler 40 on shaft 43 is adapted for rotation on two journal bearings 48 and 49 positioned with a rotational axis parallel to the optical axis of the objective lens in the objective lens barrel 30. Bearings 48 and 49 are offset with relation to the optical axis of projection lens barrel 30 a distance sufficient to permit both the refracting areas or portions 42 and 44 and non-refracting portion 46 of the scrambler 40 to be interposed across, or transversely through the light ray path 50 as shown in FIG. 1 of the drawings, and as designated by the dotted line circle 50 in FIG. 2 of the drawings. Openings 51 and are provided in the main frame 20 to permit the light ray path 50 to pass through the frame 20.

Thus, as scrambler 40 moves, or rotates on its bearing means 48 and 49, refracting portion 42, non-refracting portion 46 and refracting portion 44 may be passed successively transversely across the light ray path 50. The refracting portions 42 and 44, as will be more fully explained hereinbelow, act to scramble the light rays in the light ray path 50 to present a gray scrambled area 52 (FIG. 16) in place of the normally focused image 56 (FIG. 17) in the bright projected area 53 on the projection screen 54. When the non-refracting portion 46 replaces the refracting portion 42 in the light ray path 50, the image 56 will appear in focus and clearly visible on the projection screen 54. It is the scrambler 40, therefore, that is the heart of the invention inasmuch as it permits a clear exposure during the period when the nonrefraeting portion 46 allows the light ray path 50 to reach the screen uninhibited, and yet it renders the image 56 completely unintelligible to the observer as a gray area 52 before and after the period of exposure when the refracting areas or portions 42 and 44 respectively scramble the light rays. This is accomplished by the scrambler 40 of the invention without blurring the focus of the image bef re, during, or after exposure and without varying the intensity of illumination on the projection screen before, during, and after exposure as will be more fully explained hereinbelow.

OPERATION The movement of the mechanism in the preferred form represented in FIGS. 1 through 17 is accomplished by spring means 60 which acts to force. the scrambler 40, from an initial or first position of rest as shown in FIG. 10 of the drawings, to rotate in the direction of the arrow shown in FIGS. 11 to 13, until the scrambler 40 reaches a second position of rest as shown in FIG. 14. The scrambler 40 is held at its first position of rest (as at FIG. 10) by means of a trigger assembly 62 which holds the scrambler 40 against action of spring 60 and after the scrambler 40 moves, it is stopped at the second position of rest by the brake assembly 64.

The trigger assembly 62 comprises detent means such as a tri g r foot 66 adapted to fit into a. detent receiver or receiving means 68 on the scrambler 40 (FIG. 2). The detent receiving means 68 has a stop 70 which is adapted to cooperate with a toe portion 72 of the trigger foot 66 to define the first position of rest of the scrambler 40. The position of detent receiver 68 on scrambler 40 is determined by placing it, with relation to trigger means 62, to provide for scrambler means 40 to be in first position of rest as shown in FIG. of the drawings when toe 72 abuts stop 70. Trigger foot 66 is attached to an element such as arm'74 which is pivoted at pivot point 76 to an element such as stationary arm bracket 80 at a position on peripheral side wall 33. Movement of arm 74 on pivot 76 will remove toe 72 from stop 70 and permit spring 60 to move scrambler 40 from first position of rest toward second position of rest. Arm 74 is continuously spring urged by spring 78 which is seated against arm 74 and bracket arm 80. Thus, arm 74 may be urged toward bracket arm 80 by pressing the thumb and a finger of the operators hand against both parts respect vely to start the device by removing toe 72 from stop 70. Foot 66 may also act as a brake for the mechanism during the resetting motion when the operator moves the scrambler 40 back from second position of rest as shown in FIG. 14 to cocked, or first position of rest as shown in FIG. 10. This braking action results from foot .66 being spring pressed against a periphery portion 45 of scrambler 40 as shown in FIG. which will prevent any drifting movement of the scrambler if the hand pressure of the operator is removed. A reset handle 82 is provided to aid in resetting the device and to return the scrambler 40 to first position of rest.

As shown in FIG. 15, the trigger foot 66 holds the scrambler at periphery with non-refracting portion 46 across the light ray path 50. This position can be ascertained by moving reset handle 82 to position marker 47. Foot 66 is provided as a convenience to permit the operator to place the device positively in this position for purposes of focusing, or for purposes of explanation to viewers, at a time when the image is focused on the projection screen for a period of unlimited exposure.

BRAKE ASSEMBLY After the device is triggered by the operation of trigger assembly 62 and the scrambler 40 is accelerated up to speed, the scrambler 40 must be stopped (after exposure of the non-refracting portion 46) at a second position of rest with refracting area 44 in the light ray path 50. This is accomplished by means of the brake assembly 64. Brake assembly 64 comprises a round shaft 90 having a threaded end portion 92 'with a rectangular or keyed cross section 94 and a headed portion 106.

The brake assembly further comprises acting friction brake element 96 which includes a striker arm 98 having a striker portion 100, as well as reacting friction brake elements 102 and 104. Element 102 is the inside surface of shaft head 106, and element 104 is the inner side of wall 34. The heart of the brake assembly 64 is the acting element 96 and the reacting elements 102 and 104. A brake comprising these three elements would work satisfactorily. However, in order to improve the action of the brake as well as the wearing qualities of the brake, I provide discs 108 and 110- of a friction brake material which will lie around shaft 90 a d between elements 96, 102 and 104 as shown in 'FlG. 9 of the drawings in exploded relationship.

These elements are assembled on shaft 90, and are pressed against inner side 104 of wall 34 and held by headed portion 106 of shaft 90 against inner side 104 of Wall 34 when nut 112 is fastened to threaded portion 92 of shaft 90 against spring 114. Shaft 90 and its threaded portion 92 fit through opening 116 in wall 34. Spring 114 has a central rectangular or keyed hole 118 adapted to fit rod end 94 with some lost motion. Spring 114 is also seated snugly against rib 120 on outside of wall 34 to prevent it from rotating. The scrambler 40 is'pro- 6 vided with striker means 132 and 134 having end portions 136 and 138 respectively, adapted to strike the striker portion 100 of acting brake striker arm 98. This may be in the form of a single means having ends 136 and 138 in a proper position on the scrambler 40, or it may be in the form of separate lugs 132 and 134 as shown having the proper end portions 136 and 138, or the striker means on the scrambler may be attached to the scrambler 40 in any manner suitable to the operation of the invention. In FIG. 9 of the drawings, the device is shown in cocked position at its first position of rest, ready to be triggered, similar to the posit-ion of FIG. 10. After triggering, the scrambler 40 moves in the direction of the arrow F in FIG. 9. The extent of movement of the scrambler 40 will be approximately one-half of a revolution. As the scrambler 40 reaches the end of its forward motion (FIG. 13), striker end 136 of lug 132 will engage strike portion 100, moving striker arm 98 to cause the braking action. It is at this moment that the lost motion provided between elements 94 and 118, as indicated by double headed arrow in FIG. 7, comes into play, as follows:

LOST MOTION The tachistoscope is designed to be run at different speeds to provide for different exposures such as betw;en of a second and /4 of a second. The kinetic energy of the rotating scrambler 40 varies as the square of its velocity. There is. therefore, a vast difference in kinetic energy at the rotational speed which produces an exposure of of a second compared to that which produces an exposure of A of a second. The brake must be powerful enough to absorb the energy at the high speed without bouncing the scrambler 40 to an undesirable extent. A brake setting at the same friction would not be sensitive enough to act most efiiciently at the lower speeds.

Reference to FIG. 10 of the drawings will show the tachistoscope in cocked position. At this point, the brake has been reset and the lost motion between shaft end- 94 and opening 118 in spring 114 has been taken up in a counter-clockwise direction. The trigger is operated to start the device, and the scrambler 40 rotates in a clockwise direction as shown by the arrows in FIGS. 11, 12 and 13 of the drawings until striker end 136 of the scrambler strikes strike portion 100 of arm 98 of acting friction brake element 100, thereby causing acting element 100 to rotate in a clockwise direction.

Until the lost motion as illustrated in FIG. 7 (see double headed arrow) is taken up, reacting element 102 will rotate with acting element 96 together with shaft 90. During the taking up of the lost motion, friction occurs between acting element 96 and reacting element 104. After the lost motion is taken up, shaft can no longer rotate, and twice the friction will be enerated because reacting element 102 will be held motionless and fric-' tion will be generated by further movement of acting element 96 between it and both reacting element 102 and reacting element 104. Thus, the full friction of the brake is developed after the lost motion is taken up and only half of the friction is developed during the take-up of the lost motion. Thus, the lost motion feature makes is possible to automatically double the brake friction at high speeds compared to the brake friction generated at low speeds. If the whole friction was operative at all times, the bouncing would be more apparent at low speeds because the parts would spring more. As was said previously, the lost motion is taken up in the reverse or counter-clockwise direction when the scrambler is reset for its next operation.

Small lightweight projectors may be easily tipped over by an unbalancing force in resetting the scrambler. It is, therefore, important to keep the resetting force as small as possible when using lightweight projectors. While resetting the mechanism with the right hand, if the projector starts to tip, the natural reaction of the operator is to grab the top of the projector housing with the left hand. Since the top of the housing may be hot, the operator might be burned. In FIG. 9A of the drawings, I show a modification to the brake mechanism which permits resetting with less force. In this form of the brake mechanism, there is a shaft 901: which has a circular end 92a and a serrated nut 112a which is held firmly against rotation about shaft 90a by means of a pin 113. A spring 114a similar to spring 114 except that it has a circular opening 118a, is held against rotation by rib 120. Ratchet teeth 124 in nut 112a prevent rotation of the nut against pawls 126 in spring 114a in the direction of the arrow in FIG. 9A. However, the ratchet teeth 124 permit the nut 112a to be rotated in the opposite direction.

With the type of brake assembly illustrated in FIG. 9 of the drawings, the full friction of the brake is exerted during resetting after the lost motion is taken up. With the type of brake mechanism illustrated in FIG. 9A, only half of the friction of the brake is exerted during resetting after the lost motion is taken up. The ratchet action of the form in FIG. 9A permits the resetting, therefore, with less force than would occur without the ratchet action. When the mechanism is again triggered, the ratchet teeth 124 will hold the shaft 90 in proper position for braking action to stop the scrambler 40 at the end of its forward movement.

SPRING OPERATION Reference is now made to FIG. of the drawings to describe the action of spring 60. Spring 60 is a helical spring disposed around shaft housing 139 and having a first tail or end 140 connected to seat means 142 in a speed adjustment assembly 144. The other end or tail 146 of spring 60 bears against a pin 148 on the scrambler 40.- Thus, when the device is in cocked position as shown in FIG. 10, the spring 60 will be in position around shaft housing 139 with one end 140 seated in the speed adjustment assembly 144 affixed to a wall such as wall 36 of the frame 20, with the other end 146 of spring 60 being urged against pin 148, as shown at C in FIG. 5. There is another stop pin 150 fixed to a bracket 152 on the inner side of the shaft housing 139. |Shaft housing 139 is connected to the main frame 20 at wall 36.

Because the stop pin 150 is so mounted, it is in effect fixed with relationship to the main frame 20 whereas pin 148 will rotate with scrambler 40. Because of this relationship of construction, when scrambler 40 has rotated in the direction of the arrow to a point where pin 148 and pin 150 are both engaged by spring end or tail 146, as at S in FIG. 5, stop pin 150 will stop further circular movement of spring tail 146 and scrambler 40 will continue to rotate with pin 148 now free of any further urging by spring end 146. Thus, from the point of triggering until the point that spring end 146 reaches stop pin 150, the scrambler 40 will be continuously accelerated from a dead stop, and from that point on will continue its movement subject to being decelerated by the small forces of friction from the bearing means 48 and 49. I provide gravitational balance means, such as weighted portions 157 (as shown in FIG. 9), to counteract these small forces of friction, to maintain substantially constant rotational velocity until the scrambler 40 is stopped by the brake 62.

EXPOSURE TIME ADJUSTMENT The exposure (i.e. the time during which the clear non-refracting portion 46 of the scrambler 40 permits the image 56 to be viewed, unscrambled, on the screen) is of critical importance. The time of this exposure will be a fraction of a second. In the preferred form of the invention, the exposure time range from A to second. This range may, of course, be increased. The device has an exposure time adjustment 144 which is constructed as follows. Spring seat 142 (shown in detail in FIG. 8) is, in fact, in the form of a bolt head 159 held in place through an elongated opening 160 in wall 36 by means of a clamp nut 162. There is a bolt shaft 161, a washer 163 and a hole 165 through the bolt where the head 159 and the shaft 161 join. End of spring 60 fits into hole 165, for seating, and because hole 165 is partially in head 159 and partially in shaft 161, the washer 163 will clamp spring end 140 firmly in place when clamp nut 162 is tightened.

Opening describes the arc of a circle on a radius from the axis of bearing means 48. When spring seat 142 holds spring end 140 at a position as shown in FIG. 5 of the drawings, the device will be at its slowest speed or set to give an exposure time of A1 of a second. As spring end 140 is reset to different positions along the circle described by curved opening 160, the tension of spring 60 will be progressively increased thereby increasing the acceleration of scrambler 40 so that the greater the spring tension, the greater the speed of the scrambler 40 thereby shortening the exposure time.

I have, therefore, provided a scale designated by reference numeral 164. There is a pointer 166 on another element such as a washer 167, held in place by clamp nut 162, to show the operator of the device the various points along the scale 164 on curved opening 160 at which the clamp nut arrangement may be fixed to set the spring 160 for the speeds of the device. Scale 164 shows the designation A, and & Any other scale of speeds may be used. This scale is calibrated at the factory or elsewhere by using a spring of known strength which will operate the device at A of a second when shown in the position of FIG. 5 of the drawings, and then actually checking the device against performance for the other positions of the scale. Any calibration means known to the art may be used.

THE REFRACTING FEATURE OF THE SCRAMBLER The scrambler 40 contains refracting portion 41 with areas 42 and 44 and non-refracting portion means 46-. The refracting portion 41, when viewed in cross section as shown in FIG. 3 of the drawings, shows a lens-like arrangement which, when placed in the path 50 comprising the light rays from the objective lens (see arrow in FIG. 3), will change the direction of the light rays in said light ray path. When this is done, a visual image 56 on a screen, which would be in focus and unscrambled without the interposition of a refracting portion .41 (or its areas 42 or 44), will become scrambled as in FIG. 16, and completely unintelligible to the viewer. For example, if the visual stimuli were a series of letters or a word 56 as shown in focus on a screen in FIG. 17, the interposition of the refracting portion 42 of the scrambler 40 across light my path 50 would give the projected image the appearance as shown at reference numeral 52 in FIG. 16 of the drawings. Both effects, that as shown in FIG. 17 and that as shown in FIG. 16 would be obtained with the objective lens in a position to provide an exact focus of the projected image 56 on a projection screen 54. Thus, the change in image 56 is accomplished while the apparatus is always in a position of exact focus. Rendering the focused image 56 unintelligible, as at 52, is accomplished by the deflection of the rays 50 with the refracting mechanism of the refractor 42 with the balance of the projection mechanism being in proper position for exact focus.

The result is that the viewer will see an illuminated screen 54 having a generally grayish area 52 where the image should be, when a refracting portion is across path 50. This will momentarily resolve into a sharply focused image 56 with substantially the same screen illumination when the refracting portion is away and clear of path 50. The image 56 will then dissolve into a generaly grayish portion 52 again on white area 54 with the same intensity of screen illumination when the refracting portion 44 comes across the path 50.

Where the image 56, projected, is a word or words, these will appear as black words on a white background as shown in FIG. 17 of the drawings during the exposure, starting as a grayish area 52 as seen in FIG. 16 when the tachistoscope is in cocked position, appearing in sharp focus 56, of FIG. 17, during the exposure, and then dissolving again into the grayish area 52 of FIG. 16 after the exposure. There will be no discernible change of light intensity before, during and after the exposure, and there will be no blur due to de-focusing immediately before and after the exposure. The viewer will, however, see a gradual appearance at the beginning of the exposure and a gradual disappearance at the end of the exposure while it is always in exact focus.

When the image of this invention is caused to appear, there is no focus from a blurred, out-of-focus position which would strain the eye attempting to focus on a blurred image. The exposed image 56 produced by the tachistoscope of the invention is increased in intensity by successively allowing the light rays to assume their normal paths by moving the refracting part of the scrambler away from the path of the light beam. The reverse procedure is used to cause the image to disappear. When intelligible, the image is always in focus but varies in intensity from Zero to maximum and back to zero.'No physical eye effort is necessary to adapt to the transition from the gray area 52 to the image 56 and vice versa. In other methods, which depend upon moving a lens along the beam axis to blur out the image, the image is shown in various degrees of blur while coming into and departing from view. Eye strain caused by the viewer attempting to focus his eye on a blurred image is eliminated in applicants device.

REFRACTING LENS MEANS The refracting portion 41 of the circular type of scrambler 40 as illustrated in FIGS. 3 and 9 of the drawings (or 41a as illustrated in FIG. 18 of a second form of the invention to be described hereinbelow), may comprise a lenticular lens means. In this specification and in the claims appended hereinbelow, the term lenticular lens is defined to mean a lens having refracting surfaces other than surfaces of spheres. In FIGS. 3 and 9 (and in FIG. 18), the lenticular lens shape in cross section comprises a plurality of concave elements in each surface 170 and 172 (as shown in FIG. 3) in offset relationship. This is the preferred form of lenticular lens for use with the invention. There are many other forms of lenticular lenses which will perform satisfactorily. For example, in FIG. 3A, I show the cross section of a scrambler 40b in which surfaces 174 and 176 are substantially parallel and have a plurality of offset convex surface shapes. In FIG. 3B, I show a section of a scrambler 400 in which surface 178 has a plurality of prism shaped portions and surface 180 is planar.

The lenticular lens illustrated in the drawings are a small sample of the total number of lenses that can be designed for use with the invention. For example, the lenses shown in the drawings have a plurality of parallel elements. A lenticular lens suitable for the invention may be comprised of only one convex or concave or prism-like element.

' In FIG. 3C of the drawings, I show another form of refracting means. Referring to scrambler portions 42 and 44 in FIG. 3 will show a series of spherical lens elements 190 with the space 192 between the spherical elements 190 being rounded to be non-planar. The form of refracting means for a scrambler produced by elements 190 on a surface 192 should not be confused with the lenticular lens means just described. Although the form shown in FIG. will work satisfactorily for a tachistoscopic effect to obliterate the image 56 in accordance with the invention, the lenticular form as described above and as illustrated in FIGS. 3, 3A and 3B 10 has two additional advantages. First, it produces a smaller enlargement of the illuminated area, and second, it produces an unintelligible gray area as illustrated by reference numeral 52 in place of the image 56 when scrambled.

By scrambling the letters of a word in the direction of the longest dimension of the word, multiple images of a given letter, due to refraction, are super imposed over the adjacent letters on both sides. This makes the letters unintelligible. If the letters are only scrambled in the other direction, ghost-like images which might be intelligible might appear in the spaces above and below the word. Thus, the lenticular lens of the invention is adapted to scramble the word image in the direction of its longest dimension. The preferred deflection is an amount equal to 2 letter spaces on each side of a given letter.

In FIG. 18 of the drawings, I show another form of the invention. This form is substantially similar to the form shown in FIGS. 1 through 17 except that the scrambler 40a with its refracting means 41a moves the reciprocal translation in the direction of the double headed arrow in FIG. 18 instead of in a rotary direction. Some of the components of the form of invention in FIG. 18 have been labeled with reference numerals suffixed by the letter a, and unless some special explanation is given herein, it isto be assumed that these parts function in a similar manner to the parts of FIGS. 1 through 17 having the same reference numerals without the suffix a. For example, the scrambler 40a has refracting portion 41a which is comprised of an area 42a and an area 44a with a non-refracting portion 46a.

In FIG. 18 the scrambler is shown at its second position of rest. It is cocked by moving operating handle 82a upwardly. Operating handle 82a has a spring loaded detent end 200 which is adapted to be cammed inwardly into handle 82a by setting-cam surface 204 of trigger rod 206. Thus, when handle 82a is pushed upwardly as far as it Will go, end 200 will be cammed around and rest on the end of trigger rod 206 placing the device of FIG. 18 in cocked position. Trigger rod 206 is part of a trigger assembly 62a which has a push button 208 acting against a spring 210. Trigger rod 206 has a cutout opening 212 which is offset to end 200 when the device is in cocked position, but is in line with opening 212 when the trigger button 208 is pushed in moving trigger rod 206 in the direction of the arrow. This results in triggering the device so that it may move from a first position of rest to a second position of rest as shown in FIG. 18. This operational movement is accomplished by both the forces of gravity and the force of spring 60a and is resisted by friction approximately equal to the force of gravity. Spring 60:: acts between a speed adjustment assembly 144a and the scrambler 40a through a connecting bar 148a which serves a purpose similar to element 148 on the scrambler 40. There is a stop means 150a mounted on the main frame 20a which serves the same purpose as stop 150 in the form of the invention shown in FIG. 5 of the drawings. In other words, it limits or stops the spring action against bar 148a when hook 214 engages stop means 150a. Connecting bar 148a has, up to this point, been engaged by hook 216 to spring urge it downwardly. When hook 214 is stopped, hook 216 stops with it because both hooks 214 and 216 are part of a U- shaped system 220 which is attached to spring 60a. Thus, when the device of FIG. 18 is in cocked position, connecting bar 148a will be within the turn of hook 216. As the trigger button 208 is pushed, the scrambler 40a will start moving downwardly under spring pressure until hook 214 engages stop 150a. Then bar 148a and its scrambler 40a will continue to move downwardly Without spring assistance.

There is also a brake assembly 64a having an acting friction brake arm element 98a with a strike portion 96a which is hit by striker edge 138a to institute braking action which is similar to the braking action of the brake assembly 64 in the first form of the invention. Striker end 136a will act to reset the brake in the same manner when the device is moved back to first or cocked position.

I claim:

1. A tachistoscope comprising a main frame including a light ray pathway, scrambling means including at least one refracting portion and at least one non-refracting portion movably positioned substantially transverse the light ray pathway, together with means to move said scrambling means from a first position of rest with a refracting portion interposed in said light ray pathway to a second position of rest with a refracting portion interposed in said light ray pathway, said non-refracting portion traversing said light ray pathway for an interval of time between said first position of rest and said second position of rest of said scrambling means, and spring means acting between the scrambling means and the main frame for spring urging scrambling means from the first position of rest to the second position of rest.

2. The tachistoscope as defined in claim 1, in which said spring means bear on an adjustable seat which is movable to selected positions relative to said main frame to vary the tension of the spring to set the speed of the tachistoscope.

3. The tachistoscope as described in claim 1, in which the non-refracting portion is comprised of a transparent material having a pair of substantially parallel surfaces.

4. The tachistoscope as defined in claim 1, in which the non-refracting portion of the scrambler is provided with an opening positioned between refracting portions.

5. The tachistoscope as described in claim 1, in which said light ray pathway comprises light rays, and in which said refracting portion comprises at least one non-planar surface portion for deflecting the light rays within said light ray pathway in scrambling directions substantially within said pathway.

6. The tachistoscope as described in claim 5, in which means are provided on the non-planar surface of the refracting portion for deflecting the light rays laterally in scrambling directions.

7. The tachistoscope as described in claim 1, in which said light ray pathway comprises light rays, and in which the refracting portion comprises lens means having at least one non-planar surface area for deflecting the light rays within said pathway to scrambled positions substantially within said pathway.

8. The tachistoscope as described in claim 1, in which said light ray pathway comprises light rays, and in which the refracting portion comprises lenticular lens means for deflecting the light rays Within said pathway to scrambled positions substantially within said pathway.

9. The tachistoscope as described in claim 8, in which the light rays are projected toward a screen to form a word image and in which the lenticular lens means scrambles the word image in the direction of its longest dimension.

10. The tachistoscope as defined in claim 7, in which said scrambling means is positioned for rotation on bearing means on the main frame, and includes at least one refracting portion and at least one non-refracting portion rotating on said bearing means as parts of said scrambler.

11. The tachistoscope as defined in claim 8, in which said scrambling means is positioned for rotation on bearing means on the main frame, and includes at least one refracting portion and at least one non-refracting portion rotating on said bearing means as parts of said scrambler, and in which said lenticular lens means comprises a plurality of portions substantially concentric to the axis of rotation.

12. The tachistoscope as described in claim 1, in which there are trigger means mounted on the main frame including detent means adapted to hold the scrambler at said first position of rest.

13. The tachistoscope as defined in claim 12, in which the trigger mechanism is comprised of two elements, at least one of which is movable toward the other of said elements, each of said elements comprising a bearing surface respectively for an operators thumb and finger, said bearing surfaces being in line with each other.

14. A tachistoscope comprising a main frame including a light ray pathway comprising light rays, scrambling means including at least one-refracting portion and at least one non-refracting portion movably positioned substantially transverse the light ray pathway, together with means to move said scrambling means from a first position of rest with a refracting portion interposed in said light ray pathway to a second position of rest with a refracting portion interposed in said light ray pathway, said non-refracting portion being adapted to traverse said light ray pathway for an interval of time between said first position of rest and said second position of rest of said scrambling means, in which the refracting portion comprises lens means having at least one non-planar surface area for deflecting the light rays within said pathway to scrambled positions substantially within said pathway, and in which the scrambling means is positioned for rotation on bearing means on the main frame, and in which there are trigger means mounted on the main frame including detent means for holding the scrambling means at said first position of rest, and spring means acting against the scrambling means and the main frame for spring urging the scrambling means to rotate on said bearing means.

15. The tachistoscope as described in claim 14, in which there is a stop means on the main frame adapted to engage that portion of the spring acting against the scrambler to stop further spring action against the scrambler during the rotation of the scrambler.

16. The tachistoscope as described in claim 14 which includes braking means to stop the scrambler at the second position of rest.

17. The tachistoscope as described in claim 16 which includes a friction brake comprising at least one movably mounted acting friction brake element including a strike arm and at least one reacting friction brake element, said scrambler having striker means for striking said brake strike arm from a first direction during the forward rotation of the scrambler and striker means for striking said brake strike arm from another direction during resetting rotation of the scrambler.

18. The tachistoscope as defined in claim 17, comprising a plurality of reacting friction brake elements, at least one of which is fixed relative to the main frame, with at least another of said reacting friction brake elements being mounted on shaft means for movement relative to the main frame, said main frame being provided with stop means to limit the motion of said shaft means to a motion shorter than the motion of said acting friction brake element.

19. The tachistoscope as defined in claim 17, comprising a reacting friction brake element disposed around a shaft and fixed relative to the main frame, and another reacting friction brake element disposed around said shaft and fixed relative to the shaft, with said acting brake element positioned between and in contacting relationship to said reacting friction brake elements, said shaft having ratchet means for cooperating with pawl means associated with the main frame whereby said shaft may rotate in a direction opposite to said spring urged rotation of said scrambler, but will be held against rotation in the same direction as said spring urged rotation of said scrambler.

20. The tachistoscope as defined in claim 15, in which that portion of the spring acting against the main frame bears on an adjustable seat which is movable to selected positions relative to said main frame to vary the tension of the spring to set the speed of the device.

21. The tachistoscope as defined in claim 15, in which the scrambler rotates on hearing means and comprises gravitational balance means for counteracting the friction of said bearings to provide substantially constant rotational velocity to the scrambler after said spring is engaged by said stop means.

References Cited UNITED STATES PATENTS Lehman 352-212 Lehman 352-212 Lehman 352212 Blanton 352-212 2,840,925 7/1958 Dunson 35-352 3,018,686 1/1962 Kurz 351-31 3,021,751 2/1962 Barnette 351-31 DAVID SCHONBERG, Primary Examiner P. A. SACHER, Assistant Examiner U.S. C1.X.R. 

